The Uber car service, which operates in London, Manchester and in other countries, equips it drivers with a smartphone app which works out fares by being connected to a remote server.

The app takes into the account the time taken and the distance travelled, just like a black cab meter. Uber makes its money by typically taking around 20 percent of its drivers' fares.

Only black cabs licenced by TfL are allowed to use fare meters in London under law. TfL believes that as the Uber smarphone app is not physically connected to the vehicle, like the meters in black cabs, the app is legal - but it wants a "binding" legal ruling from the High Court.

But the Licensed Taxi Drivers Association (LTDA), which represents the black cab drivers, insists the app equates to being a taximeter, which private vehicles are not allowed to use in London.

The LTDA is not being appeased by TfL going to the High Court, and says its drivers will demonstrate against the Uber app on 11 June, by bringing gridlock to central London streets.

Uber, which is backed financially by Google, said it welcomed TfL's move to try and settle the matter at the High Court. But the company is also facing opposition to its service from licenced cab drivers in Milan, Paris and nationally in Spain. Earlier this year, Uber's service was banned in Brussels.

Leon Daniels, TfL's managing director of surface transport, said, "As in many other areas of transport and retail services, apps can offer passengers the potential of better and more convenient services.

He said, "We have carried out the largest compliance operation in our history to ensure that the highest standards are being maintained. On the issue of taximeters, the law is unclear and we have taken a provisional view.

"We will be asking the High Court to provide a binding ruling. This is the sensible approach, and we hope that London's taxi drivers and private hire drivers and operators will work with us to bring clarity on this issue."

Steve McNamara, head of the LTDA, told the BBC, "Our beef is not with Uber but with the regulator which is not enforcing the law and kowtowing in the face of Uber's money."

He claimed, "The reason for the complete collapse of a normally strong and vigilant regulator can only be put down to the fact that TfL are intimidated by the money, power and influence being brought to bear by the enormous presence of Uber's backers Google and Goldman Sachs."